CONFIG_CPU_PXA168 is not available for thedefaultarchitecture x86.
Result is shown for architecture arm

CONFIG_CPU_PXA168 (not configurable)

modulename: pxa168.ko

and/or

clk-pxa168.ko

configname: CONFIG_CPU_PXA168

Linux Kernel Configuration
└─>Marvell PXA168/910/MMP2/MMP3
└─>CPU_PXA168
In linux kernel since version 2.6.30 (release Date: 2009-06-09)  
Select code specific to PXA168

source code:
arch/arm/mach-mmp/pxa168.c

depends
CONFIG_ARCH_MMP

is selected by
CONFIG_FB_PXA168